function [image, size] = loadEnviData( fname )
% freadenvi           - read envi image (V. Guissard, Apr 29 2004)
%
%     Reads an image of ENVI standard type 
%    to a [col x line x band] MATLAB array
% image=freadenvi(fname)
% [image,p]=freadenvi(fname)
% [image,p,t]=freadenvi(fname)
%
% INPUT :
%
% fname string giving the full pathname of the ENVI image to read.
%
% OUTPUT :
%
% image----------- c by l by b array containing the ENVI image values organised in
%    c : cols, l : lines and b : bands.
% p  1 by 3 vector that contains (1) the nb of cols, (2) the number.
%    of lines and (3) the number of bands of the opened image.
%
% t  string describing the image data type string in MATLAB conventions.
%
% NOTE :    freadenvi needs the corresponding image header file generated
%    automatically by ENVI. The ENVI header file must have the same name
%    as the ENVI image file + the '.hdf' exention.
%
%%%%%%%%%%%%%


    % Check user input
    if ~ischar(fname)
        error('fname should be a char string');
    end
    
    % Parameters initialization
    elements={'samples ' 'lines   ' 'bands   ' 'data type '};
    d={'bit8' 'int16' 'int32' 'float32' 'float64' 'uint16' 'uint32' 'int64' 'uint64'};

    % Open ENVI header file to retreive s, l, b & d variables
    rfid = fopen(strcat(fname,'.hdr'),'r');
    
    % Check if the header file is correctely open
    if rfid == -1
        error('Input header file does not exist');
    end

    % Read ENVI image header file and get p(1) : nb samples,
    % p(2) : nb lines, p(3) : nb bands and t : data type
    while 1
        tline = fgetl(rfid);
        if ~ischar(tline), break, end
        [first,second]=strtok(tline,'=');
    
        switch first
            case elements(1)
                [f,s]=strtok(second);
                p(1)=str2num(s);
            case elements(2)
                [f,s]=strtok(second);
                p(2)=str2num(s);
            case elements(3)
                [f,s]=strtok(second);
                p(3)=str2num(s);
            case elements(4)
                [f,s]=strtok(second);
                t=str2num(s);
                switch t
                    case 1
                        t=d(1);
                    case 2
                        t=d(2);
                    case 3
                        t=d(3);
                    case 4
                        t=d(4);
                    case 5
                        t=d(5);
                    case 12
                        t=d(6);
                    case 13
                        t=d(7);
                    case 14
                        t=d(8);
                    case 15
                        t=d(9);
                    otherwise
                        error('Unknown image data type');
                end
        end
    end
    fclose(rfid);

    t=t{1,1};
    % Open the ENVI image and store it in the 'image' MATLAB array
    disp([('Opening '),(num2str(p(1))),('cols x '),(num2str(p(2))),('lines x '),(num2str(p(3))),('bands')]);
    disp([('of type '), (t), (' image...')]);
    fid=fopen(fname);
    image=fread(fid,t);
    image=reshape(image,[p(1),p(2),p(3)]);
    fclose(fid);
    size=p;
    


